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    <title>Document</title>
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        var b=10;
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        var a="20";
        var b="10";
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        var a=20;
        var b=10;
        console.log(a+b);
        var a=20;
        var b="10";
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        var myname="sally";
        var b="我的名字是"+myname;
        console.log(b);
        var myname="'sally'";
        var b="我的名字是"+myname;
        console.log(b);
        var myname="sally";
        var b="我的名字是'"+myname+"'";
        console.log(b);

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